1. Field of the Disclosure
The invention relates to an assembly for monitoring parameters of a gas turbine engine, in particular using the resistance of a carbon fibre raft mounted to the engine.
2. Description of the Related Art
A typical gas turbine engine has a substantial number of electrical components which serve, for example, to sense operating parameters of the engine and/or to control actuators which operate devices in the engine. Such devices may, for example, control fuel flow, variable vanes and air bleed valves. The actuators may themselves be electrically powered, although some may be pneumatically or hydraulically powered, but controlled by electrical signals.
Electrical power, and signals to and from the individual electrical components, is commonly transmitted along conductors. Conventionally, such conductors may be in the form of wires and/or cables which are assembled together in a harness. In such a conventional harness, each wire may be surrounded by an insulating sleeve, which may be braided or have a braided cover.
By way of example, FIG. 1 of the accompanying drawings shows a typical gas turbine engine including two conventional wiring harnesses 102, 104, each provided with a respective connector component 106, 108 for connection to circuitry, which may be for example accommodated within the airframe of an aircraft in which the engine is installed.
The harnesses 102, 104 are assembled from individual wires and cables which are held together over at least part of their lengths by suitable sleeving and/or braiding. Individual wires and cables, for example those indicated at 110, emerge from the sleeving or braiding to terminate at plug or socket connector components 112 for cooperation with complementary socket or plug connector components 114 on, or connected to, the respective electrical components.
Each conventional harness 102, 104 comprises a multitude of insulated wires and cables. This makes the conventional harness itself bulky, heavy and difficult to manipulate. The conventional harnesses occupy significant space within a gas turbine engine (for example within the nacelle of a gas turbine engine), and thus may compromise the design of the aircraft, for example the size and/or weight and/or shape of the nacelle.
Conventional harnesses comprise a large number of components, including various individual wires and/or bundles of wires, supporting components (such as brackets or cables) and electrical and/or mechanical connectors. This can make the assembly process complicated (and thus susceptible to errors) and/or time consuming. Disassembly of the conventional harnesses (for example removal of the conventional harnesses from a gas turbine engine during maintenance) may also be complicated and/or time consuming. Thus, in many maintenance (or repair or overhaul) procedures on a gas turbine engine, removal and subsequent refitting of the conventional electrical harness may account for a very significant portion of the operation time and/or account for a significant proportion of the potential assembly errors.
The electrical conductors in the conventional harnesses may be susceptible to mechanical damage. For example, mechanical damage may occur during installation (for example through accidental piercing of the protective sleeves/braiding) and/or during service (for example due to vibration). In order to reduce the likelihood of damage to the conductors in a conventional harness, the protective sleeves/braiding may need to be further reinforced, adding still further weight and reducing the ease with which they can be manipulated. Similarly, the exposed electrical connectors used to connect one conductor to another conductor or conductors to electrical units may be susceptible to damage and/or may add significant weight to the engine.
In addition to the electrical systems, a gas turbine engine comprises various other systems that are critical to and necessary for the functioning of the engine. Such systems include, for example, fluid systems including gas and liquid systems.
In general, the components of the various support systems (such as electrical and/or fluid systems) that are provided to the engine are referred to as engine dressings. At least some of the engine dressings are conventionally provided on casings of a gas turbine engine, such as a fan case. Conventional arrangements of engine dressings, in which the various systems and components thereof are individually attached to the engine in a number of different manual operations are time consuming, susceptible to errors, and may result in at least some parts of the dressing being damaged.
A gas turbine engine is also provided with various dedicated systems/components that measure engine parameters, for example during operation. For example, the gas turbine engine may comprise temperature sensors (such as thermocouples), fire detectors (such as elongate elements, for example pressurized tubes or electrical capacitors, that run over the engine), strain gauges and vibration detectors. These monitoring systems may be used to measure performance of the engine and its components and/or to detect wear and/or failure. However, the monitoring systems further add to the complexity, part-count, weight, and build-time of the engine.